RFR: 8295191: IR framework timeout options expect ms instead of s

[Eric Nothum]

The flags `-DTestCompilationTimeout` and `-DWaitForCompilationTimeout` expect values in ms. The example in the README was misleading as one could infer from "default: 10s" that the flag expects values in ms. Therefore I changed the values and units in the example to ms.

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Commit messages:
 - Update README.md
 - change s to ms in README.md

Changes: https://git.openjdk.org/jdk/pull/14649/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14649&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8295191
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/14649.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14649/head:pull/14649

PR: https://git.openjdk.org/jdk/pull/14649